Carb Kits - A Comparison
Posted: Tue Oct 11, 2011 7:23 pm
A Forum dedicated to the early Honda GoldWings
And thanks to jethro1954 for the Barracuda carb kits. Without those I wouldn't have anything to compare.Intellectual Property Notice: All material appearing in this website is the property of Randall Washington, and is protected under United States and international copyright laws. The photographs, text and other content may not be copied, reproduced, distributed, stored, or manipulated in any manner without the express written permission of Randall Washington.
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This tells me that this kit is NOT correct for the 769A's.Saber cycle wrote:Honda never made OEM carburetor rebuild kits but sold each component by piece. Carb kits were an aftermarket creation of which Napco and Keyster were the most popular brands. Our kits compare to the Napco kits, which were the most complete on the market.
Carburetor repair kit to rebuild one OEM 1978 or 1979 GL1000 Keihin carburetor model IDs 769A and 771A. Owners of non-emissioned control 1978 may have to reuse their primary main and slow air jets.
Here's a new problem to worry about if your decide to use aftermarket float valves:Randakk wrote:If you don't know the prior history of your carbs, identify the status of your current float valves. OEM seats have Keihin logo marks and a "1.0" flow rating mark…otherwise, they are aftermarket
One nice thing about the OEM float valve set from Honda is that it also includes the inlet screen, which is not provided with any aftermarket GL1000 float valves.
In the past, problems arose with bad batches of aftermarket float sets which had valve needles that were too short. These were either manufacturing errors or packaging mistakes. In these cases, no matter how high you set the floats, the valves would never close completely. Flooding was inevitable. There is still some risk if you purchase aftermarket float sets that you will receive merchandise from these prior bad lots.
For the float valves the 'plunger' in the Barracuda is shorter than the other two and the retaining clip is shorter to compensate. It's seat is also the only one not size marked. The tip on the OEM "plunger" appears rounded while the aftermarkets are squared off. Using a welding tip cleaner as a gauge (use what I have), the Keyster and OEM seats measured the same. The Barracuda, however, allowed two sizes larger to pass thru. And of course the OEM is the only one with a filter screen. Left to right Barracuda, Keyster, OEM.Randakk wrote:If you need the float needle and seat assembly...
The only way to go is OEM Honda. These are pricey, but easily last 25 years and 100,000 miles. Honda also includes the inlet fuel screen with their set (very important!). I don't know of another source for these screens. They are not available separately and not included with aftermarket sets. Also, aftermarket float valve and seat sets are notorious for leaking!
Observation shows differences. The lengths and points are not the same. Don't think either aftermarket are suitable as a replacement for OEM.Randakk wrote:Recently, I've discovered some improperly sized jet needles that were provided with aftermarket carb rebuild kits. The needles looked identical to the original but did in fact have a significantly narrower cross section at the mid-point of the tapered section. Effectively, this made the needles much richer. The brand in question is NAPCO and the kits were for a '76 which happens to be one of my bikes. The result of these improper needles was the bike in question ran fine near sea level (although a plug check showed it was running slightly rich in the mid-range and the fuel mileage was terrible). The real problem showed up at altitude...I spent 3 days riding on the Blue Ridge Parkway in NC at elevations ranging from 2000-6000 feet. The bike was fine below 4000 feet elevation, but above this elevation it would foul all 4 plugs in about 20 minutes of riding (at sustained 4000 rpms!). I know from prior trips that this particular bike always ran fine at these altitudes. Suspecting the recently installed aftermarket needles, I measured them when I got home and sure enough they were significantly undersized...thereby flowing too much fuel at a given midrange throttle position.
Like the Napco, the Barracuda air jets have no size markings and the markings on the packages are subject to falling off. Using the tip cleaner as a gauge, the 60's measured the same, but all the other sizes were smaller when compared to the OEM. On the 'top hat' at the bottom it can be clearly seen that it doesn't have the part that goes inside the emulsion tube, making it like one piece. Left to right Barracuda, Keyster, OEM.Randakk wrote:Caution: the NAPCO kits contain 3 jets which are identical except for the orifice size: idle air, primary air and secondary air jets. They are NOT stamped with the jet size on the jet as OEM jets are. These 3 jets come in individual plastic bags with labels indicating the jet size. It would be very easy to screw up the placement of these jets so be careful out there. However, in my experience, jets and jet needles rarely wear out, so you may not need them.
That alone is enough to convince me to only use the reinforced gaskets, which Barracuda and Napco do not have. Also note that the Barracuda gasket (left in photo) has narrower and uneven sides. They may have removed some material to alleviate the gasket "creep" flooding problem. I think it would do the opposite and make the gasket weaker and more problematic.Randakk wrote:The Keyster gaskets are laminated with an integrated layer of fiber reinforcement to provide size / shape consistency which prevents distortions in use. The Napco version does not have this fiber reinforcement and are made from a different type of synthetic rubber. Both types of gaskets are certified for use with "normal" gasoline blended with ethanol...like E10 or E15. Both Keyster and Napco market their wares under a variety of brands and private labels.
For whatever reason, some portion of the NAPCO gaskets seems to be overly reactive with gasoline...possibly susceptible to ethanol (or other oxygenating agents) and sometimes swells when exposed to fuel. The problem is that occasionally the gasket can swell to the point that float operation can be affected. The symptom is sudden, severe flooding in recently overhauled carbs that performed perfectly when first put back into service. The curious thing is this seems to occur in isolated cases...most are fine.
Other contributing factors based on my research:
The problem seems to originate in areas where ethanol blends are more prevalent and have higher concentrations.
Slightly under-torqued float bowl screws contribute to the problem, This permits the gaskets to "creep" inward when the clamping pressure is too low. I realize that this is a dangerous thing to mention as these screws are easily stripped!
Slightly mis-aligned float ...when splayed outward, they are less tolerant of gasket "creep"
One case involved the admitted introduction of forbidden E85!
Curiously, some batches of fuel (from different gas stations) that I tried did not cause the swelling which makes me certain that some aspect of fuel composition is the culprit.